A braking catch device for elevators is known from EP 0 899 231 A1. The known braking catch device comprises a bracket which engages around a guide rail for an elevator car and is arranged in transverse direction with respect to the guide rail. In addition, two brake jaws supported on the bracket are arranged at both sides of the guide rail. One of the brake jaws serves as an active brake jaw. The other brake jaw serves as a passive brake jaw. In that case, the active brake jaw is supported by way of a work eccentric, which is connected with a rolling disc to be secure against relative rotation. The rolling disc and the work eccentric are rotatable about a common fulcrum pin. In that regard, the rolling disc and the work eccentric together form a cohesive actuating element. When triggering takes place, the rolling disc is brought by initial rotation into frictional contact with the guide rail and the rolling disc is thereby further rotated by the still-moving elevator car. The entire braking catch device is thereby drawn in such a way that the passive brake jaw comes into contact with the guide rail. Through further rolling of the rolling disc, the active brake jaw is also led up to the guide rail by way of the work eccentric. After stopping of the elevator car the engaged safety brake can be released again by opposite movement of the elevator car and consequent return rotation of the rolling disc.
The following problems arise in the case of use of a safety brake (braking catch device) for elevator installations, such as is known from, for example, EP 0 899 231 A1. Setting and checking of the safety brake device is usually required for reliable operation within the scope of legal requirements or other specifications at the time of first placing in operation and in a given case also at regular or individually determined intervals in time, such as, for example, in the case of regular maintenance or after emergency braking. Determination of braking slide in a test run is of substantial importance in the context of such checking and setting. In the case of such a test run, for example, a specific load and a specific speed of the elevator car at the instant of triggering of the safety brake can be predetermined. Through pressing of the brake jaws against the guide rails, stress tracks, which in principle can be measured, arise on the guide rails. However, it has proved that such braking tracks or stress tracks are, in practice, often poorly visible. In particular, the exact start point and end point are often difficult to recognize. A supposed possibility consists of coloring the guide rails in the relevant region in order to produce clearer tracks. However, the colorant used then influences friction behavior and thus braking slide. The mentioned processes or methods thus have the common disadvantage that the determined braking slide is liable to a significant degree of inaccuracy or a significant degree of measurement error or that even functioning of the brake can be influenced.